The present invention relates generally to inclinometers, and more particularly, to night vision compatible inclinometers for use in vehicles, such as aircraft, in which night vision goggles may be worn by the pilot.
Inclinometers are also known as slip indicators, turn-and-bank indicators, and electronic leveling indicators. Traditionally, inclinometers have been used on aircraft to indicate the attitude, or inclination to the horizontal of an axis of the aircraft at any instant in flight. Known inclinometers have included a type which is comprised of a liquid filled capsule having a ball suspended within. The pilot can ascertain the plane's attitude from the location of the ball within a viewing area or window of the capsule.
Historically, the ball within the inclinometer has been made of a ceramic material. However, ceramic material will not work with night vision equipment. Night vision green light (NVIS Secure Lighting) directed at ceramic material will cause the ceramic to scintillate. The scintillating ceramic will cause a pilot's night vision goggles to be excited which reduces the sensitivity of the goggles and impairs the pilots visibility.
Military specification MIL-L-85762A sets forth the requirements for "lighting, aircraft, interior NVIS compatible" equipment. This military specification is incorporated by reference herein.
The inclinometer of the present invention is designed to work with NVIS equipment. The present invention preferably comprises two NVIS secure lamp modules, a liquid capsule having a damping fluid therein (preferably alcohol), and a suspended ball which is preferably a spherical white zirconium oxide material (zirconia). The background of the capsule is preferably a dark or black color. The damping fluid is a fluid which preferably meets military specification MIL-C-5020, which is also incorporated by reference herein.